This is just my first draft so I would like thoughts and opinions about all of it. I have my reasons for each piece but i'm not attached to most of it not even the names. The overall feel is to give solid two weapon fighting with a complexity level somewhere between the Champion and Battlemaster. Aaaaaaaaaaand GO!

Martial Archetype
Dervish

(3rd) Ambidexterity- Your extra attack from two weapon fighting no longer uses your bonus action. You now make two attacks when you make an attack of opportunity, one with each hand. This only applies if you are wielding a light or finesse weapon in each hand.

(7th) Instinctive Defense- While not wearing armor and wielding a light OR finesse weapon in each hand your armor equals your Int+dex.

(10th) Uncanny Feint- At the end of your turn, while wielding a light or finesse weapon in each hand, you can choose one enemy you have attacked this turn to have disadvantage against the next attack that targets it.

(15th) Defensive Flourish- While you are wielding a light or finesse weapon in each hand you may use your reaction to impose disadvantage to one spell attack roll against you.

(18th) Fast Mind- When you use your action surge you add your intelligence bonus to the damage of all your melee attacks until the start of your next turn. You also add your intelligence bonus to any saving throw that you use your indomitable feature on.